Journal of Mathematical Analysis and Applications, cilt.371, sa.2, ss.414-424, 2010 (SCI-Expanded, Scopus)
For every weakly statistically convergent sequence (xn) with increasing norms in a Hilbert space we prove that supn{short parallel}xn{short parallel}/√n < ∞. This estimate is sharp. We study analogous problem for some other types of weak filter convergence, in particular for the Erdös-Ulam filters, analytical P-filters and Fσ filters. We present also a refinement of the recent Aron-Garcia-Maestre result on weakly dense sequences that tend to infinity in norm. © 2010 Elsevier Inc.